1. Field of Invention
This invention relates generally to chemical dispensing systems and specifically to a method and system for flushing chemicals from a liquid chemical delivery system.
2. Description of Related Art
Liquid chemical delivery systems are used to automatically deliver a plurality of viscous chemicals to one or more destinations. Examples of a liquid chemical delivery system having a single manifold and a single distribution tube and the advantages thereof are described in commonly owned U.S. Pat. No. 5,014,211, incorporated herein by reference. FIG. 1 shows a chemical delivery system 100 of the type disclosed in U.S. Pat. No. 5,014,211. When it is desired to deliver a chemical stored within the container 102 to, for instance, the washer 110, the chemical pump 142 is operated in a forward direction so as to pump the chemical from the container 102 into the manifold 130. The transport pump 132 pumps the chemical from the manifold 130 to the destination washer 110 via the feed tube 150. In some embodiments, the transport pump 132 has a larger pumping capacity than the chemical pump 142 and therefore draws water into the manifold 130 from the break tank 116 while pumping the chemical from the manifold 130 to the feed tube 150. In this manner, chemicals from the container 102 are diluted before being delivered to the washers 110-112.
After one or more chemicals are successfully delivered to the washers 110-112, it is desirable to flush the chemical pumps 142-146 with water to remove residual chemicals therein. Thus, after delivery of a chemical from the container 102 to the washer 110, the corresponding chemical pump 142 is operated in a reverse direction to pull water from the manifold into the chemical pump 142 and thereby remove any chemical residual within the pump 142. Minimizing the time that the pump 142 is exposed to chemicals sourced from the container 102 maximizes the useful life of both the chemical pump 142 and its associated pump tube.
In an industrial laundry system such as, for instance, system 100 of FIG. 1, it is desirable to use highly concentrated detergents in order to minimize storage and transportation costs. However, high concentration detergents such as, for instance, the commercially available detergent xe2x80x9cCLAX Ultima,xe2x80x9d are non-ionic surfactant chemicals that tend to thicken or xe2x80x9cgelxe2x80x9d when exposed to water. Thus, flushing the chemical delivery system 100 with water immediately after a non-ionic surfactant detergent is delivered using the system 100 may be problematic. Specifically, water is likely to flow into the chemical supply containers 102-106, and therefore likely to come into contact with the detergent therein, while respective pumps 142-146 are operated in the reverse direction. The resultant gelling of a non-ionic surfactant detergent at or near the outlet of the containers 102-106 may not only compromise the proper concentration of the detergents therein but also lead to a blockage of that outlet and, thus, disrupt subsequent detergent flow from the supply containers 102.
Prior xe2x80x9csolutionsxe2x80x9d to problems resulting from this xe2x80x9cgellingxe2x80x9d of non-ionic detergents are not entirely satisfactory. Some solutions simply avoid the use of chemicals that gel upon contact with water. This approach, however, undesirably limits the range of chemicals that may be used with the delivery system 100. Other solutions include using a non-flushed chemical injection system, or using steam injection systems, to flush the chemical pumps 142-146. These approaches, however, are complicated and expensive.
A supply tube isolation system is disclosed for use with a chemical delivery system having a manifold connected to one or more chemical pumps which, in turn, are connected to corresponding supply containers via supply tubes. Present embodiments include feedback tubes connected between the manifold and each of the supply tubes of the delivery system. A controllable valve means is provided at or near the junction of the feedback tube and the supply tube so as to effectively segment the supply tube into first and second portions, where the first supply tube portion is that which is connected between the valve means and the manifold, and the second tube portion is that which is connected between the valve means and the supply container.
While one or more chemicals are being delivered to predetermined destinations within the delivery system, the valve means is positioned so as to allow a forward pumping action of the chemical pumps to effect chemical flow from corresponding supply containers to the manifold via the supply tubes and chemical pumps, and thereafter to the predetermined destinations via a feed tube. After the chemical is successfully delivered, the valve means is positioned so as to allow a reverse pumping action of the chemical pumps to draw water from the manifold into the chemical pumps and then back to the manifold via the first portions of the supply tube and the feedback tube. The second portions of the supply tubes are closed and thereby isolate the chemicals stored in the supply containers from the water. In this manner, present embodiments allow the chemical pumps and supply tubes of a suitable chemical delivery system to be flushed with water without exposing chemicals stored within the supply containers to water and, therefore, without an undesirable gelling of non-ionic surfactant chemicals.